124 DENTALIUM-COMPRESSIDENS. 



II. Shell strongly curved, but little compressed, densely obliquely 

 striated, the length 8'5 mill., about 4j times the greatest diam- 

 eter, West American, simplex, p. 125. 

 III. Shell decidedly curved, length 9 to 9^ times the greatest diam., 

 a. Length 12-16 mill., faintly finely striate longitudinally ; 

 Antillean. o2)hiodon, p. 126. 

 a'. Length 11 mill,, circularly wrinkled ; Australian, 



platycerus, p. 126. 



D. PREssuM Sharp & Pilsbry, n. n. PI. 22, figs. 50, 51, 52 ; pi. 7, 



fig. 11. 



Shell small, slightly and evenly curved, thin, considerably taper- 

 ing, the tube strongly compressed between its convex and concave 

 sides, almost subangular on the lateral sides. White, somewhat 

 shining. Sculpture : faint, low, regular, longitudinal riblets with 

 very shallow intervals, crossed at right angles by close, "sharp, 

 irregular scratches in the line of growth," bent forward on the con- 

 cave side of the tube, which is also faintly wrinkled in the same 

 direction toward the larger end. Aperture decidedly oblique, oval, 

 the arc along the concave side generally less curved than the rest of 

 the peristome. Apical orifice oval, without slit or notch. 



Length 12, greatest diam. of aperture 2, least 1*75 mill., diam. at 

 apex 75 mill. (S. & P. type). 



Length 0'45, greatest diam. at aperture 0*06, least 0*05 inch., 

 diam. at apex 0019 inch = 11-25, 1-5, 1-25, 0475 mill. (Watson's 

 type). 



N. of Culebra Island, West Indies, 390 fms. (Challenger). Off 

 Cape San Antonio, in 413 fms. ; near St. Vincent, in 424 fms. 

 (Blake). Gulf of Mexico between Mississippi River delta and Cedar 

 Keys, Fla., Ill fms. (Albatross). Thirty-three and one-half miles 

 S. of Rebecca Shoal, lat. 24.° 02' N., long. 82° 31' 80", 430 fms. (Dr. 

 W. H. Rush). 



D. compressum Wats., Journ. Linn. Soc. London., xiv, p. 516 



(1879) ; Chall. Rep., p. 9, pi. 1, f. 9.— Dall, Bull. M. C. Z., ix, p. 38 



(1880) ; Ibid., Blake Rep., p. 426 ; Bull. U. S. Nat. Mus., No. 37, p. 

 76. Not D. compressum Orb., Prodr. Paleont. Strat., i, p. 233, no. 

 135 (1850). 



As Dall remarks, the posterior half of well-preserved specimens is 

 coarsely obscurely striated. This is variable, however, in specimens 

 of the same age and condition, and sometimes almost imperceptible. 



